The invention relates generally to preparation of sodium chloro-aluminate, and particularly to an improved process for the preparation of high purity sodium chloro-aluminate.
A battery is a component used to store a portion of the energy in mobile systems such as electric vehicles and hybrid electric vehicles (for example locomotives, off-highway mining vehicles, marine applications, buses and automobiles), and for stationary applications such as uninterruptible power supply (UPS) systems and “Telecom” (telecommunication systems). The high-temperature sodium/metal halide electrochemical cells are generally targeted for use in industrial transportation, telecommunication, and uninterruptible power supply (UPS) batteries. These cells could potentially offer high energy density, high power density, longer cell life, and lower cost-requirements for many of these applications.
Sodium/nickel chloride batteries are one of the most widely used batteries among the many types of sodium/metal halide batteries. Sodium/nickel chloride batteries utilize molten sodium as the anode, nickel chloride as the cathode, and molten sodium chloro-aluminate (alternately sodium tetrachloroaluminate, NaAlCl4) as a secondary molten electrolyte in the cathode.
Production of NaAlCl4 normally includes reacting aluminum chloride with sodium chloride and then purifying the product obtained to the required grade to be used in a sodium/nickel chloride battery. Fabrication of a large batch of NaAlCl4 usually takes 2-3 days' time until a sufficiently pure, clear colorless melt is formed. Impurities in the electrolyte reduce battery performance and may result in rupture of the cell. Sufficient information is not available about any in-situ determination of the reaction completion or the determination of the amount of impurities present in the formed product. It would therefore be desirable to develop a commercial method for the speedy production of NaAlCl4 with accurate measurement of reaction completion and in-built measures for purifying the NaAlCl4 product and measuring the impurity level of the product.